Clopidogrel is an anti-platelet medication approved by the U.S. Federal Drug Administration (FDA) for use in patients who undergo Percutaneous Coronary Intervention (PCI) with coronary stent implantation. Anti-platelet medications work to prevent blood clots from forming. Some studies have suggested that patients who have a certain genetic liver enzyme abnormality (known as cytochrome P450 2C19 [CYP2C19] *2 or *3 allele) may have a reduced ability to activate clopidogrel, and therefore may have a lowered response to clopidogrel. It is thought that perhaps people who have a coronary stent procedure may have this genetic liver enzyme abnormality. There is a research genetic test available to determine whether or not someone has this genetic liver enzyme abnormality. Ticagrelor, is a newer anti-platelet drug that is not dependent on the CYP2C19 liver enzyme for its activation and hence in poor clopidogrel metabolizers, alternative drugs like Ticagrelor have been recommended for use as an anti-platelet agent after PCI. The purpose of this study is to determine if genetic testing can identify the best anti-platelet therapy, for patients who undergo a coronary stent placement and do not activate clopidogrel very well.